GB2196736A

GB2196736A - Liquid level sensor

Info

Publication number: GB2196736A
Application number: GB8725432A
Authority: GB
Inventors: Dennis Michael Treu
Original assignee: Cobe Laboratories Inc
Current assignee: Terumo BCT Inc
Priority date: 1986-10-30
Filing date: 1987-10-30
Publication date: 1988-05-05
Anticipated expiration: 2007-10-30
Also published as: DE3736715C2; DE3736715A1; CA1290043C; GB8725432D0; FR2606143A1; JPS63121716A; US4744808A; JP2557418B2; GB2196736B; FR2606143B1

Description

GB2196736A 1

SPECIFICATION um/waste pump 24, and electronic controller

26, connected to receive signals from level Fluid flow apparatus sensor 40 and to control valve 16 and control other components (not shown) of the dialysate The invention relates to fluid flow apparatus. 70 preparation machine. Pumps 22, 24 are posi- It may be desirable to sense and control the tive displacement gear pumps.

level of a liquid flowing through a ' fluid flow Heater/deaerator 20 includes tubular flow chamber. For example, in a deaeration cham- passage 28, which surrounds heating element ber of dialysate preparation apparatus, if the 30 and overflows into passage 32 on the left level of liquid goes below the outlet, air re- 75 side of baffle 34 between the heating zone in moved from the liquid will be undesirably passage 28 and deaeration chamber 36. Dea pumped downstream with the water. eration chamber 36 includes polypropylene According to the present invention, there is particles (spheres and cylinders approximately provided fluid flow apparatus comprising: a 0.090"-0.2286cm in diameter) that are pre housing defining a chamber having a chamber 80 vented from flowing beyond screens 38 lo inlet and a chamber outlet for flow of liquid cated below level sensor 40. At the top of therethrough; a float in said chamber; and a deaeration chamber 36 is bleed valve 42 magnet and a magnetic position sensor; one blocking flow of liquid through gas outlet 44 of said magnet and magnetic position sensor connected to vacuum/waste pump 24.

being carried by said float for movement with 85 Referring to Figs. 2-6, level sensor 40 in- the change in liquid.level in said chamber, and cludes float 46 mounted for floating up and the other of said magnet and magnetic posi- down along vertical guide support 48 between tion sensor being fixedly mounted with re- base plate 50 and overhanging portion 52 at spect to said housing. the top of guide support 48. Guide support In preferred embodiments, there is a verti- 90 48 is mounted at the top of the housing for cally oriented guide support along which the deaeration chamber 36 and has central bore float travels as the liquid level in the chamber 54 in which hall effect sensor 56 (an inte changes; the magnetic position sensor is car- grated circuit available from Sprague Electric ried by the guide support, and there are two Company, Concord, New Hampshire, under the magnets in the float on both sides of the 95 trade designation UGN 3501T) is received and guide support; the magnets have their north supported by horizontal floor 58.

and south poles vertically arranged with re- Magnets 60, 62 are received within pockets spect to each other, the north pole of one 64, 66 of base 68 of float 46. Top 70 covers magnet being on top and the north pole of the top of base 68 and has hole 72 there- - and 100 through aligned with central bore 74 of base the other magnet being on the bottom, the guide support is attached to the top of 68, for receiving vertical guide support 48.

the chamber housing. Magnets 60, 62 are each made of shunt bar The invention is hereinafter more particularly 76 (0.500"-1.27cm long, described by way of example only with refer- '0.062"-0. 15748cm thick, ence to the accompanying drawings, in which: 105 0.187"-0.47498cm wide with full radius Fig. 1 is a schematic of a deaeration portion ends and made of CR steel, ASTM A366) and of a dialysate preparation machine; two rare earth metal magnetic disks 78 Fig. 2 is a diagrammatic perspective view of (0.062"-0.15748cm thick, a liquid level sensor of a, deaeration chamber 0. 187"-0.47498cm diameter, samarium co 17 of the Fig. 1 apparatus, 110 balt grade 18, magnetized to 8700 internal Fig. 3 is an exploded perspective view of gauss, approximately 1200 gauss at surface).

the Fig. 2 level sensor; Water entering from inlet 12 passes through Fig. 4 is a vertical. sectional view, taken at pressure regulator 14, which provides protec- 4-4 of Fig. 3, of a guiddl support of the Fig. 2 tion from large line pressure variations, and level sensor, 115 solenoid valve 16, which is alternately opened Fig. 5 is a top view, partially broken away, and closed and has a 6- second period. The of a float of the Fig. 2 level sensor, and duty cycle of valve 16 is controlled by con- Fig. 6 is a vertical sectional view, taken at troller 26 so as to be open a portion of the 7-7 of Fig. 6, of the Fig. 6 float. 6-second period depending upon the liquid Referring to Fig. 1, there is shown appara- 120 level indicated by the output voltage from tus 10 for deaerating water used in a dialyslevel sensor 40.

ate preparation and supply machine of the Water flows through heat exchanger 18, re- type shown in Jonnson U.S. Patent No. ceiving heat from the spent dialysate, and en 4,371,385. It includes inlet 12 for receiving ters heating passage 28, flows upward in it, tap water, inlet pressure regulator 14 (ad- 125 spills over into passage 32 and flows under justed to have an outlet pressure of 6 psi baffle 34 into deaeration chamber 36. The when its outlet is not connected to a further liquid in heater/deaerator 29 is. subjected to pressure reducer), two-position (open-closed) negative pressure by deaeration pump 22, solenoid valve 16, heat exchanger 18, heat- which pumps at a fixed rate higher than the er/deaerator 20, deaeration pump 22, vacu- 130 inflow rate, and by vacuum pump 24. Pump 2 GB2196736A 2 22 is operated at a fixed voltage to pump at said guide support is mounted at the top of a constant rate (the value of which can be said housing.

Claims

adjusted by the operator), and pump 24 is 4. Apparatus according to Claims 2 or 3, operated to pull on the air in chamber 36 to wherein said float has an opening through maximize the vacuum in chamber 36, without 70 which said guide support passes. overpowering pump 22. The negative pressure 5. Apparatus according to any preceding and increased temperature cause volatilization claim, wherein said magnet has its north and of dissolved gas from the liquid. Plastic par- south poles vertically oriented with respect to ticles between screens 38 provide nucleation each other and spaced from each other by a sites at which air bubbles form. Gas accumu- 75 gap between them along a vertical axis, and lating above the liquid surface passes through wherein said magnetic position sensor pro valve 44 and pump 24 while average liquid vides an output signal with a magnitude re level is maintained constant by level sensor lated to the level in said chamber. 40. 6. Apparatus according to Claim 4, wherein Magnets 78 are spaced from each other, 80 said magnetic position sensor is carried by thereby increasing the range of liquid levels in said guide support, and there are two mag chamber 36 over which level sensor 40 has a nets carried by said float on opposite sides of linear output. The opposite polarity between said magnetic position sensor. opposing magnets and the use of rare earth 7. Apparatus according to Claim 6, wherein magnets cause a concentrated magnetic flux 85 said magnets have north and south poles ver at the location of sensor 56 between oppostically oriented with respect to each other and ing magnets 78, contributing to accuracy of spaced from each other by a gap between sensor 40. The level in chamber 36 is con- them along vertical axes, and one said magnet stantly changing owing to the cycling of valve has its north pole on the top, and the other 16, but the level is kept within the desired 90 said magnet has its north pole on the bottom, range. The level of liquid is maintained above and wherein said magnetic position sensor the active elements of heating element 30. provides an output signal with a magnitude Deaerated water supplied by pump 22 to related to the level in said chamber. the remainder of the hydraulic circuitry of the 8. Apparatus according to Claims 6 or 7, dialysate preparation machine is mixed with 95 wherein each said magnet comprises a pair of dialysate concentrate and provided to the dia- individual magnetic elements mounted on a lysate side of a dialyzer. Spent dialysate re- vertically oriented shunt bar, one said indivi turns from the dialyzer to inlet 27 of heat dual magnetic element having its north pole exchanger 18, and is removed via vacuum/- against said shunt bar and the other said indi waste pump 24. 100 vidual magnetic element having its south pole Other embodiments are feasible. For against said shunt bar. example, level sensor 40 could be connected 9. Apparatus according to Claim 4 or any to a digital switch that switches to high/low claim appendent thereto, wherein said guide outputs as its threshold voltage is passed, support has stop members larger in size than and used, for example, in an air separator in a 105 said opening to retain said float between spent dialysate flow path upstream of a bal- them. ance chamber. It should also be understood 10. Apparatus according to any preceding that although the invention has been specifi- claim, wherein said chamber has a gas outlet cally described hereinabove by way of referat the top of said housing for removing gas ence to a dialysate preparation medicine, the 110 volatilized from said liquid. invention can equally well be applied to other 11. Apparatus according to Claim 10, fur- forms of fluid flow apparatus. ther comprising a divider in said chamber di viding it into a deaeration zone including said CLAIMS float and an upstream heater zone.

1. Fluid flow apparatus comprising: a hous- 115 12. Fluid flow apparatus substantially as ing defining a chamber having a chamber inlet hereinbefore described with reference to and and a chamber outlet for flow of liquid there- as shown in the accompanying drawings.

through; a float in said chamber; and a mag net and a magnetic position sensor; one of Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from said magnet and magnetic position sensor be- The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3 RD.

ing carried by said float for movement with Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

the change in liquid level in said chamber, and the other of said magnet and magnetic posi tion sensor being fixedly mounted with re spect to said housing.

2. Apparatus according to Claim 1, further comprising a vertically oriented guide support along which said float travels as the liquid level in said chamber rises and falls.

3. Apparatus according to Claim 2, wherein